Oil and natural gas can be produced from wells having porous and permeable subterranean formations. The porosity of the formation permits the formation to store oil and gas, and the permeability of the formation permits the oil or gas fluid to move through the formation. Permeability of the formation is essential to permit oil and gas to flow to a location where it can be pumped from the well. Sometimes the permeability of the formation holding the gas or oil is insufficient for the desired recovery of oil and gas. In other cases, during operation of the well, the permeability of the formation drops to the extent that further recovery becomes uneconomical. In such cases, it is common to fracture the formation and prop the fracture in an open condition using a proppant material or propping agent. Such fracturing is usually accomplished by hydraulic pressure. The proppant material or propping agent is typically a particulate material, such as sand and (man-made) engineered proppants, such as resin coated sand and high-strength ceramic materials (e.g., sintered bauxite, crystalline ceramic bubbles, and ceramic (e.g., glass) beads), which are carried into the fracture by a fluid.
Further, for example, if relatively light weight, porous crystalline ceramic (e.g., alumina) proppants are used, fluid (e.g., the fracturing fluid) can penetrate into the proppant increasing its density, which can in turn can adversely affect the flow of the proppant into the fractured areas.
There continues to be a need for additional proppant options, preferably, proppants with improved properties. Also, for example, there is a desire, particularly for relatively light weight, porous proppants, to prevent, or at least reduce, penetration of fluids into the proppants.